High electromagnetic field levels of household appliances (such as washing machines and hair dryers) and wireless devices (such as laptops and routers) may be at least partially to blame for the rise in childhood obesity in recent years, according to a 13-year study by Kaiser Permanente that followed hundreds of pregnant women and 733 of their children.

De-Kun Li
Kaiser Permanente

After controlling for several factors, including child gender, pre-pregnancy BMI, maternal age at delivery, race, education, breastfeeding, and smoking, researchers write in Nature's Scientific Reports that children exposed to high in-utero levels are nearly twice as likely to be overweight or obese as children exposed to low in-utero levels.

Specifically, high levels were considered to be more than 2.5 milligauss (mG), which is a unit of magnetic field strength, while low levels were considered to be less than 1.5 mG, and medium was everything in between. (The Environmental Protection Agency has compiled a list of magnetic field measurements in everyday electrical devices.)

"Pregnancy is a critical developmental stage that is among the most vulnerable periods to environmental exposures," De-Kun Li, a perinatal epidemiologist and the lead author of the study, said in a news release. "EMF exposure during pregnancy could impact the fetal development, including endocrine and metabolic systems, predisposing offspring to higher risk of obesity...This finding could have implications for possibly reducing childhood obesity and better understanding the obesity epidemic."

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When breaking the study down into the 18 factors considered, the findings are a bit befuddling. Out of all areas studied, including maternal, prenatal, and childhood factors, researchers found that only family income and childhood habits of eating fruits and vegetables varied among the low, medium, and high maternal exposure groups.

It turns out that children who ate more fruits and veggies tended to have a mother with higher magnetic field exposure during pregnancy. Researchers said they could not explain this association. And oddly, the pattern of exposure according to family income was inconsistent: Women with low or high family income had lower exposure than women with medium family income.

The study comes on the heels of Dr. Li's previous work showing that electromagnetic fields could play a role in pregnancy outcomes and childhood diseases such as asthma. Still, he stresses that the results need to be replicated by additional studies.

About the author

Elizabeth Armstrong Moore is based in Portland, Oregon, and has written for Wired, The Christian Science Monitor, and public radio. Her semi-obscure hobbies include climbing, billiards, board games that take up a lot of space, and piano.
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